Hydraulic table reciprocating mechanism



Oct. 31, 1944. F. E.-JOHN$ON 2,361,349

HYDRAULIC TABLE RECIPROCATINCT MECHANISM Filed Feb. 10, 1942 2 Sheets-Sheet 1 55 i I] H 17 IO 100 99 FRANKLIN E. JOHNSON Ill Oct. 31, 1944. F. E. JOHNSON 2,361,849

Filed Feb. 10. 1942 2 Sheets-Sheet 2 I22 i 28 FRANKLIN E.-JuH-su/v 10 f M tate grinding'of a shouldered work piece.

. ing operation. Otherobjects will be in Patented Oct. 31, 1944 HYDRAULIC TABLE RECIPROCATIN G MECHANISM 4 Franklin E. Johnson, Worcester, Mass, assignor to Norton Company,Worcester, Mass., a corporation 01' Massachusetts Application February 10, 1942, Serial No. 430,234.

3. Claims.

The invention relates to grinding machines, and more particularly to ahydraulically operated table reciprocating mechanism.

' One. object of the invention. is to provide a simple" and thoroughly practical hydraulically operated grinding machine. Another object of the invention is to provide an improved hydraulically operated table reciprocating mechanism. Another object of the invention is to provide a hydraulically operated table reciprocating mechanism which may be stopped and reversed at precise predetermined positions to facilitate a shoulder grinding operation.

A further object of the invention is to provide a hydraulically operated table reciprocating mechanism, in which the table is stopped by a positive stop at a precise predetermined position, after which the table reverses. A furthe) object of the invention is to provide a hydraulically operated table reversing mechanism which is stopped by a positive stop when reversed either manually or by table dogs to facili- A further object of the invention is to provide a hydraulically operated table reciprocating mechanism which may be positively stopped at reversal by a positive stop mechanism andin which the table speed is reduced prior to stopping and reversing to facilitate table reversal. A further object of the invention isto' provide a. hydraulically operated table reversing mechanism which is arranged so that the rapidly reciprocating table is slowed down prior a reversal of flow of fluid to facilitate reversing at a predetermined position for a shoulder grindpart obvione or in part pointed out hereinafter.

The invention accordingly consists in the features of construction; combinations of elements, and arrangements of parts, as will be exemplitied in the structure to be hereinafterdescribed, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings in which is shown one of various possible embodiments of the mechanical features of the invention,

Fig. I is a hydraulic diagrammatic illustration of a grinding machine table reciprocating mechanism;

2 is a fragmentary front elevation of a grinding machine embodying the invention;

Fig. 3 is across sectional: view, taken approximately' on. the line 3-4! of Fig. 2; and

Fig. 4 is a fragmentary vertical sectional view, on enlarged scale, taken approrrimately on the line 4-4 of lever.

. A grinding machine has been illustrated in the drawings, comprising a base l which supports a longitudinally reciprocable' work supporting table II on a V.-way l2. and a flat way l3 for a. longitudinal reciprocatory movement relative to the base I0. A fluid pressure mechanism is provided for reciprocating the work table Fig. 3, through the table stop H. A fluid pressure cylinder [5 is supported by cylinder head brackets l6 and I1 fixedly mounted on theunder side of the table II. The cylinder contains a pair of spaced pistons l8 and l9 which are connected by a pair of hollow piston. rods 20 and 2|, respectively, witha pair of hollow brackets 22 and 23, respectively, which are fixedly mounted on the opposite ends of the base Ill. i l

A fluid pressure system is provided for supplying fluid: under pressure to the cylinder [5. This system may comprise a reservoir 25 contained within the base II of the machine, A motor driven fluid pump 26 draws fluid: from the reservoir 25 through a-pipe 21 and forces fluid under pressure. through a pipe 28 to a table reversing valve 29. 'I'hertable reversing valve 29 is a pistontype reversing valve comprising a valve stem 30 having formed integrally therewith valve' pistons 3|, 32 and 33. Fluid under pressure passing through the pipe 28 enters a passage 34 in-the reversing valve 29 and, in the position of the valve (Fig. 1), enters a valve chamber 35 locatedbetwe'en the valve pistons 3| and 32 and passes out through a passage 36, a pipe 31, through a chamber 38 in the bracket 22, through the hollow piston rod 20, into a cylinder chamber 3-9 to move the cylinder l5 and table II toward the left (Fig. 1). During this movement, fluid within a cylinder chamber 4! is forced out through the hollow piston rod 2t, through achamber 4| within I the bracket 23-, through a pipe 42 and a pasage 43, into a cylinder chamber 44 located between the valve'plstons 32 and 3-3, respectively, and passes out througha pipe- 45 in. a manner to be hereinafter described and returns to the reservoir 25.

The reversing valve 29 may be shifted manually by means of a pivotally mounted control lever 46 which is supported on a; .stud4'l which also supports at its inner'end a downwardly projecting lever 48. A pin 49 ismounted on the lower end of the lever 48 and is connected with the valve stem 30; If it is desired to reverse the direction of movement of the table H manually, the control lever 46 is shifted manually in a clockwise direction into broken line position 46a to reverse the position of the valve 29 so that fluid under pressure from the pipe 28 passes into the valve chamber 44 and through the passage 43 and the pipe 42 to the cylinder chamber 40 to move the cylinder I and the table II toward the right (Figs. 1 and 2). The reversing valve 29 may be shifted either manually as above described or automatically by fluid under pressure, as will be hereinafter described.

In order to attain the main object of the invention, a positive stop mechanism is provided whereby the table II is precisely stopped at each reversal in a predetermined position so as to facilitate grinding up to and adjacent to a shoulder on a cylindrical work piece. A pivotally mounted lever 50 is supported on a stud 5| on the base III which is in turn fixedly mounted relative to the base I 0. The stop lever 50 is provided with an inwardly projecting pin 52 which is arranged in the path of a pair of adjustably mounted table dogs 53 and 54. The table dogs 53 and 54 are adjustably supported by a T-slot 55 formed in the front edge of the table II. A pair of adjustable stop screws 56 and 51 are supported in brackets 58 and 59, respectively, which are in turn fixedly supported relative to the base Ill. and 51 are arranged to be engaged by stop surfaces 60 and BI, respectiVely Which are formed on a cam plate 62 which is preferably formed as an integral part of the lever 50.

It will be readily apparent from the foregoing disclosure that when the table I I which is traveling toward the left (Fig. 1) approaches the end of its stroke, the dog 54 will engage the .pin 52 and rock the stop lever 50 in a counterclockwise direction. This movement continues until the stop surface 6| engages the end of the stop screw 51 which serves positively to limit the longitudinal movement of the table II toward the right. Similarly, if the table II is traveling toward the right, this movement continues until the table dog 53 engages the Din 52 and rocks the stop lever 56 in a clockwise direction. This rocking movement of the stop lever 50 continues until the stop surface 60 engages the end of the adjustable stop screw 56 so as to positively limit the longitudinal movement of the table II toward the right. The swinging movement of the stop lever 50 serves in a manner to be hereinafter described to control the fluid pressure system so The stop screws 56 as to reverse the flow of fluid under pressure to ing screw 63 is provided for clamping the parts of the lever 59 with the pin 52 in the path of the dogs 53 and 54. The stop lever is normally held in a central or vertical position by means of a tension spring 65, one end of which is connected to a stud 66 carried by the plate 62 of the lever 50. The lower end of the spring is fastened to a stud 61 which is fixedly mounted to a part fixed relative to the base III.

A cam face 68 on the lower end of the cam plate 62 is arranged to actuate a slow-down valve 69 which is mounted on the front of the base II). The slow-down valve 69 is a piston type valve comprising valve pistons 10 and II. A compression spring I2 normally serves to hold the valve pistons Ill and II in an uppermost position with an adjustable follower I3 in engagement with the cam face 68. The follower I3 is formed as a screw threaded member which is screw threaded within the piston I0 and arranged so that the follower surface thereof may be adjusted relative to the piston, thus serving to vary the position of the pistons I0 and 'II relative to the cam face 68 and thus varying the action of the valve 69. Fluid exhausting from the table reversing valve 29 through the pipe 45 enters a port connected to the chamber located between the valve pistons I0 and II of the slow-down valve 69 and passes out through a port connected to the exhaust pipe I4 and a pipe I5 into the reservoir 25,

It will be readily apparent from the foregoing disclosure that when the stop lever 50 is moved in either direction either by the table dog 53 or 54, the valve pistons I0 and II will be moved downwardly so as to gradually cut off the exhaust of fluid passing from the pipe 45 into the pipe I4 to gradually slow down the speed of the work table .II before the stop lever 50 engages either the stop screw 56 or 51. By adjustment of the follower I3, the slow-down valve 69 may be regulated so that it gradually cuts off a portion of the exhaust of fluid from the pipe 45 as desired.

In order to facilitate manual control of the table movement, it is desirable to provide a start and stop valve for starting and stopping the movement of the table I I. A start and stop valve integral with the casing of the table reversing valve 29 (Fig. 3) isprovided, which is a piston type valve comprising a valve stem 8| having formed integrally therewith valve pistons 82, 83 and 84. A manually operable start and stop le- .ver 85 is pivotally supported by a stud 86 which is in turn supported by a bracket 81 fixedly mounted relative to the base Ill. This start and stop valve 80 is substantially identical with that shown in the prior U. S, patent to Wallace H. Wood, No. 2,071,677 dated Februar 23, 1937, to which reference may be had for details of disclosure not contained herein. -In the position of the valve 80 (Fig. 1), fluid exhausting through the pipe I4 enters avalve chamber 88 and passes unrestricted through the exhaust pipe I5 into vthe reservoir 25. When it is desired to stop the table movement, the lever 85 is rocked in a clockwise direction (Fig. 1) to shift the valve stem BI toward the right so that the bevelled end surface 89 of the valve piston 84 closes a V-sbaped port 90. The valvestem 8I may be manually rotated by a knob 9| to facilitate adjusting the bevelled end surface 89 in relation to the V- shaped port 90 when in an open position so as to control the rate of exhaust of fluid from the pipe I4 and thus control the speed of the longitudinal movement of the table I I,

In order to maintain the desired operating pressure in the fluid pressure system, an adjust- .able pressure relief valve 96 is connected to the pipe line 28 so that excess fluid under pressure within the pressure pipe 28 may be returned directly through a pipe 97 into the reservoir 25. A second adjustable pressure relief valve 98 is connected in the pipe line 28. This second relief valve may be set for a slightly lower pressure than the relief valve 96. and is arranged so that when the Valve 69 is? closed either manually or during reversalof the table, a back pressure is built up in the system which opens the relief valve98 and passes fluid under pressure in a manner to be hereinafter described to actuate the reversing valve 29 by fluid under pressure, The

relief valve 98 is connected by a pipe 99 with the valve 80. Inthe position of the valve 80 (Fig.1), fluid passing throughthe pipe-99 enters a valve chamber I located between the valve pistons 83 and 84 and passes outwardly through a pipe IOI toa control va1veI02. The control valve I02 is a piston type valve which is connected by a link I03 with the piston 1 00f the slow-down valve 69 so that when the slow-down valve 69"is depressed during reversal, a movable piston I04 having a groove which engages the forked end of the link I03 or the valve I02 is moved downwardly so that fluid under pressure passing through the pipe II'II enters a valve chamber I05 in the valve I02 and passes outwardly through a pipe I 06, through a shuttle type control valve I 01. The shuttle type valve N11 is actuated by pressure fluid from the reversing valve 29. Thepi-pe 31 which passes fluid under pressure to the cylinder chamber 39 is connected by means of a pipe I08 with an end chamber I09 in the valve I01 so that when fluid under pressure is passed through the pipe 31 with the parts shown in the position illustrated in Fig. 1, fluid under pressure will pass through the pipe I08 into t e end chamber I09 to movei'a valve piston II II toward the left into the position illustrated in Fig. 1. Similarly, the pipe 42. which leads to the cylinder chamber 40 is connected 'by means of a pipe III with an end chamber H2 at the left-v when the valve I02 is depressed, fluid under prcs' sure passing through the pipe I06 passes through a pipe II3, through a valve chamber IILout through a pipe H5, andthen passes through a selector valve IIS which will" be hereinafter described, and out through a pipe I-I1-' which con-- veys fluid under pressure to an. end chamber III] in the table reversing valve 29 to shift the reversing valve stem 30 toward the right (Fig. 1') so as to reverse the flow of fluid passing to'the table actuating cylinder I5. apparent from the disclosure as shown in Fig. that no fluid passes into the and chamber H8 during the normal stroke of the table II sincethe control valve I02 is normally closed, except when actuated by the table actuated stop lever 50 at the end of the table stroke; The valve I02 is provided to prevent actuation of the reversing valve 29 during the normal reciprocatory stroke of the table II caused by a sudden increase in pressure within the system suflicient to open the relief valve 98. The valve I02 (Fig. 1) prevents passage of fluid by the relief valve 98 to the shuttle valve I01.

Similarly, when the table I I is travelling in the opposite direction, fluid under pressure passin through the pipe I06 passes through a pipe H9 and through a valve chamber I which will then bepositioned to coincide with the port at the end of the pipe H9 and passes through a pipe I2I,

through the selector valve I it, and through a pipe I It will be readily,

I22 to convey fluid under pressure: to an end chamber I23 at the right-hand end of the reversing valve 29 to shift the valve stem 30 toward the left. (Fig. 1) to reverse the valve 29 and thus changethe direction of flow of fluid to the table cylinder I5, 'It will thus be seen that the shuttle valve I01servesi to control the passage of fluid under pressure automatically to the proper end chamberrIIB or I23 of. the table reversing valve 29 when the stop lever 50zis actuated to initiate a table reversal.

In order to permit a manual control of the table reciprocatinglmovement; the selector valve H6 is provided with an actuating knob I25 which is mounted on the outer end of the valve stem I26 to control the admission to or exhaust of fluid from the end-chambers I I 8 and I 23, thereby controlling the movement of the table reversing valve 29 hydraulically or manually. The. valve stem I261 has a valve piston I21 formed integrally therewith. The valve piston I21. is a hollow type piston having a central chamber I23. In the position of the valve piston I2l (Fig. 1),, fluid under pressure passing through the pipe I I5 may pass directly through the selector valve H6, into the pipe, I I1. Similarly, fluid under pressure passing through the pipe I2I may pass directly throughthe selector valve I I6 and into the pipe I22, as above described. When it is desired to control the reciprocating or traversing movement of the table. I I. manually by manual actuation of the reversing valve 29, the knob I25 of the valve H6 is moved toward the right (Fig. 1), which movement cuts. off fluid under pressure within the pipe H5 or the pipe. I'2I, so that the pipe H1 is connected with a port I29 and the pipe I22 is connected with a port. I30 so that fluid within the end chambers H8. and I23 may readily pass through pipes H1 and I22 and through the central aperture I28 in thevalve piston I21. Thus a direct by-pass of fluid between the end chamber H8. and the end chamber I23 is formed so that the reversing valve 29 may be readily shifted manually to control. the longitudinal movement of the table II..

When. the table II approaches the end of its reciprocatory stroke, the valve 69 is gradually and partially closed by a rocking movement of the stop lever 59; as abovedescribed, which serves partially to cut off the exhaust of fluid from the table cylinder I5 to slow down the table'movement prior to the engagement of the stop surfaces 60 orIiI with the stop screws 56 or 51, respectively. After the tablereversing valve, 29 has shifted. it is desirable that the flow or" fluid be unrestricted through theexhaust pipe 14 sothat the table I I may be started rapidly in the reverse direction or adjusted from dwell control to grinding .wheel infeedat the end of the table stroke at both ends. In order to accomplish this desirable result, a shuttle type valve I is provided, comprising a. pair of spaced" integralvalve pistons I36 and I31, forming a valve chamber I39 therebetweem i 'When fluid under pressure is passed} through the pipe 31 to the cylinder chamber 39, fluid under pressure may also 'pass through a pipe I39 into a valve chamber I40 to shift the valvepistons I33 and I31 to the extreme right-hand end position (Fig. l). The movement of the valve pistons I36 and I31 toward the right is limited by means of an adjustable stop screw MI. Similarly; when fluid under pressure is passed through the pipe 42 to the cylinderchamber 40,

fluid under pressuremay also: pass through a pipe I42, into an end chamber I43, to move the valve pistons I31 and I36 toward the left into an extreme left-hand end position, the left-hand end position being determined by means of an adjustable stop screw I44. The rate of movement of the valve pistons I36 and I31 may be regulated by means of a valve I45 in the pipe line The shuttle valve I35 serves upon reversal of the direction of flow of fluid to the table cylinder I to shunt fluid around the slow-down valve 69, thus allowing a quick unrestricted exhaust of fluid from the pipe 45 to facilitate a quick pickup of the table movement in the reverse direction. The exhaust pipe 45 is connected to an adjustable valve I46 by' a pipe I41 to the shuttle valve I35, so that during the longitudinal shifting movement of the valve pistons I36 and I31, fluid may'exhaust through the pipe I41, through the valve chamber I38, and out through a pipe I48, thus shunting the exhaust around the slow-down valve 69 to instantaneously allow a quick pick-up movement of the table I I in the reverse direction before the spring 65 has had time to return the valve pistons and H to their uppermost position. The valve I46 in the pipe I41 serves as an additional means of regulating the flow of exhaust fluid. By shutting off the valve I46, the shuttle valve I35 may be rendered inoperative in case it is desired to reverse the table I I without utilizing the shuttle valve I35.

For certain grinding operations, it may be desirable to provide a more rapid reverse action so that the efiect of the slow-down valve 69 may be rendered inoperative. A manually operable valve I50 is provided, comprising a manually operable knob I5I mounted on the outer end of a valve stem I52. A pair of valve pistons I53 and I54 are formed integral with the valve stem I52. The exhaust pipe 45 leading from the table reversing valve 29 is connected by a pipe I55 with the valve I50. A pipe I56 connects the valve I50'with the exhaust pipe 14. If it is desired to render the effect of the slow-down valve 69 inoperative, the knob I5I is rotated 90 degrees so that exhaust fluid in the pipe 45 may flow through the pipe I and through a passage I51 which extends transversely through the valve piston I53 so that it may pass out through the pipe I56, the pipe 14, through the V-port 90, into the valve chamber 88, and out through the exhaust pipe 15, into the reservoir 25, thus shunting the exhaust fluid around the valves I35 and 69.

It may also be desirable during the operation of the machine to reverse the table II during its normal reciprocatory stroke. In order to accomplish this result, the fluid pressure pipe 28 is connected by means of a pipe I58 with the valve I50 and a pipe I 59 is connected between the valve I50 and the pipe 99. A manually operable knob I 60 which is formed as an integral part of the link I03 is provided for manually actuating the valves 69 and I02 when desired. If it is desired to reverse the table movement during a normal reciprocatory stroke, the operator may push the knob I5I to shift the valve I50 into its right-hand end position (Fig. 1) and at the same time manually depress the knob I60 to shift the valves 69 and I02 which serves to provide a slowing down and reversal of the table.

In this position of the valves 69 and I02, fluid from the pump 26 passing through the pipe 28 will pass through the pipe I58, through a valve chamber I6I, and out through the pipe I59,

through the pipe 99, the valve chamber I00, the pipe IOI, through the valve chamber I05, the pipe I06, through the pipe II3, the valve chamber II4, the pipe II5, through the selector valve H0 and the pipe II1, into the end chamber II8 to shift the table reversing valve 29 into its reverse position. A compression spring I62 normally serves to hold the valve I50 in the position illustrated in Fig. 1. If a rapid reverse movement is desired during the normal strok of the table II, the knob I5I may be rotated ninety degrees and at the same time moved manually toward the right while the valves 69 and I02 are depressed, thus causing a shifting of the table reversing valve 29 and at the same time allowing fluid to be shunted around the valves I35 and 69 and directly into the reservoir 25 so that a quick manually controlled reverse movement of the table I I may be obtained.

The table II may also be reversed during a normal reciprocatory stroke without actuation of the valve I50, if desired. The knob I60 may be depressed to shift the valves 69 and I02 downwardly which serves to cut off exhaust of fluid from the table cylinder, thereby to build up a back pressure in the fluid pressure pipe 28 which opens the relief valve 98 and passes fluid under pressure through the pipe 99, the valve chamber I00, the pipe IOI, the valve chamber I05 in the valve I02, and through the valves I01 and H6 to shift the reversing valve 29 into a reverse position.

It is desirable to provide means whereby fluid may readily by-pass from the cylinder chamber 39 into the cylinder chamber 40 when the hydraulic table traversing or reciprocating mechanism is stopped to facilitate a manual adjustment of the table I I when'desired. A pipe or passage I65 connects the passage 36 in the table reversing valve 29 with a port I66 in the start and stop valve 80. When the start and stop lever is shifted in a clockwise direction (Fig. 1) to close the V-port to stop the hydraulic movement of the table II, a valve chamber I61 moves into alignment with the port I66 and a port I68 so that fluid may readily pass from the pipe I65, through the valve chamber I61, and through a pipe I69 which connects with the passage 43 in the-table reversing valve 29 and which connects with the pipe 42 leading to the cylinder chamber 40. It will thus be readily apparent that when the start and stop valve 00 is shifted to a table stop position, fluid may freely by-pass from the cylinder chamber 39 to the cylinder chamber 40 and vice versa without changing the setting of the shuttle valves I01 and I35, as the control lever 46 should not be touched during manual adjustment of the table II.

The operation of the improved table reciprocating mechanism will be readily apparent from the foregoing disclosure. Assuming all of the parts to have been previously adjusted and the table I I is traveling in the direction of the arrow (Fig. 1), that is, toward the left, this movement of the table II continues until the table dog 54 engages the pin 52 and rocks the table stop lever 50 in a counterclockwise direction so that the stop surface 6! engages thev stop screw 51 which positively stops the table I I in a predetermined position so as to facilitate the grinding of a work piece up to and adjacent to a shoulder.

During the rocking movement of the table stop lever 50, the follower 13 is gradually moved downwardly by means of the cam face 68 on the cam plate 62, causing a downward movement of the a ve i on 10 and H to i artial y cu oi?! th exh ust offlu di qm t e ta c linde c amber.

pipe II5, through the selector valve 1 I5 and the.

pipe Ill, o theend chamb r lla he ta l reversing valve 29 to shift the table reversing va-lve into its reverse position, i I

t wil b e i ap arent r mathe for oin i e o ureth t w the t ble os 5 reeksthe table stop lever 50, the table ,,II is raduall slowed d wn b f t e t ps rfac i! en a e th st p crew 51 p t e y t etopthe able II in a pr dete mined p s o a te 'wh ehth able ever ing valve 2 is sh ted to ch ng the thre tion of flow of fluid under pressure so as to start the table I I moving in the reverse direction. When t va ve 9 is shi ed int a ht-bend nd posit on by f u d und r p ssure. uid om the pipe 28 then passes through the valve chamber 44,, the passage .43, the pipe 42,.into the cylincler chambe tosta t th tabl I m v es a d tion toward t e righ F 1 A t e se ne time fluid under pressure passing through the pipe 42 passes through thepipe I I I, the valve I32, into the end chamber II2 of the shuttle valve I01, to shift the shuttle valve piston I I0 into its right-hand end position so that it is positioned for the next table reversal. fluid under pressure passes through the pipe 42, it also passes through the pipe I42 into the end chamber I43 of the shuttle valve I35 to shift the valve pistons I36 and I3! toward the left (Fig. 1) at a rate of movement as governed by the valve I45. As the port I38 passes the ports at the ends of the pipes I41 and I48, unrestricted exhaust of fluid may by-pass around the slow-down valve 69 through the chamber I38, the pipe I48, into the reservoir IIJ, thus allowing a quick pick-up of the table in its movement toward the right. During this shifting movement of the shuttle valve I35 and the by-passage of fluid therethrough, the table I I moves away from the dog 54 so that the released tension of the spring 55 will allow the lever 50 to return to a vertical position (Fig. 1) and the slow-down valve under the influence of the compression spring 12 to move upwardly to the position shown in Fig. 1, so that thereafter unrestricted exhaust of fluid passing through the pipe 45 may pass through the slow-down valve 69 and the pipe I4 into the reservoir I3. The table II continues its movement toward the right (Fig. 1) until the adjustable table dog 53 engages the pin 52 to rock the table stop lever 50 in a clockwise direction to bring the stop surface 60 into engagement with the stop screw 56 thusto positively stop the table II from moving toward the right. Thereafter the relief valve 98' opens due to back pressure within the system which operates in a manner above described to convey fluid under pressure through the fluid pressure system into the end chamber I23 of the table reverse valve 29 to shift it toward the right into the position shown in Fig. 1 again to reverse the direction of movement of the table II. It will thus be seen that a hydraulic table reciprocating At the same time e erseto accu ately me s a v il; Pi ce re ativ oil-1 op rating te When t is desi e t top th hyd a l mo emen f he ab e" l't set and sta t lever 8 may e sh ii d ill a s ekw se d r ct ve e- 1 i0 5 t l ert 89. thus c this ff the B BF PWF 9f luid 9!!! the n ire em and th re y e. ii -s he recip o ng m vement sf the ta l Mr F u d item h end chamb rs H? and 13 of the ab e reve n a ve 28 m y ex au t th eves either the valve chamber I14 or I29, respectively, f thesh ttl valve I 0 dep din r e it pos ies and Peer. o wa d b vs a Pi e 1 1 W h exhaus s tum C 33 it? th I $QWQ F A Pair o ad ustab e valve i l and Ill le a in he P n 1m item theslmtt valve to] a e nd p nden l to e u ate he esh sst at fluid remeit e the end chambe H8 o t ens hamb r s es i s v ti l1 S rvi to QQ TQ- th rat of hittin o the ta le re ers n valve H durin reversals? that he per od reve ma eresuls d a de r d- If i is d i d is op ate he t ble H by t ualsast eti ti o the o t ol e e 45, h kno 0f the selector valve I I5 moved toward the right s- 1, hich mov men shi ts th va e stem I26 so that a direct by-pass ,of ti d obtained etw enth ensinsilsmbeie We Q 23 st t tablaevers n val A? $9 thetih eb e e s-e valve may be readily shifted under the control .of the manually operable control lever 46, thus facilitating a manual controlled movement of the table II either for a grinding wheel truing operation or otherwise, as desired.

It will thus be seen that there has been provided by this invention apparatus in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. In a grinding machine having a base, a longitudinallyreciprocable table, means including a piston and cylinder to reciprocate said table; a reversing valve therefor, fluid chambers in the ends of said valve whereby admission of fluid under pressure thereto serves to reverse the same, a source of fluid under pressure, means including adjustable table dogs and fixed stop screws positively to limit the reciprocatory movement of the table in either direction, a slow-down valve actuated by said dogs to throttle the exhaust of fluid from said cylinder at reversal gradually to slow down the table, an adjustable pressure relief valve, connections between said relief valve and the source of fluid under pressure, means including connections between said relief valve and the mechanism has been provided whereby the table end chambers of said reversing valve whereby positive stopping of the table serves to build up a back pressure to open said relief valve and admit a reversing valve therefor, fluid chambers in the ends of said valve whereby admission of fluid under pressure thereto serves to reverse the same, a source of fluid under pressure, means including adjustable table dogs and fixed stop screws to limit the reciprocatory movement of the table in either direction, a pivotally mounted control lever which is actuated by said dogs, a slow-down valve which is actuated by movement of said lever to slow down the table movement, as it approaches the end of its stroke by throttling the exhaust of fluid from said cylinder, an adjustable pressure relief valve, connections between said relief valve and the source of fluid pressure, means including connections between said relief valve and the end chambers of said reversing valve whereby positively stopping of the table serves to build up a back pressure to open said relief valve and admit fluid under pressure to an end chamber of the reversing valve to shift the reversing valve and thereby reverse the direction of movement of the table, and a shuttle valve which is operatively connected to the slow-down valve so as to by-pass fluid around said slow-down valve at the beginning of the table movement and/or during reversal to facilitate a rapid starting of the table in the reverse direction.

3. In a grinding machine having a base, a lonactuated by said dogs to throttle the exhaust of gitudinally reciprocable table, means including a piston and cylinder to reciprocate said table, 'a'

reversing valve therefor, fluid chambers in the ends of said valve whereby admission of fluid under pressure thereto serves to reverse the same,

- a source of fluid under pressure, a, pivotally mounted stop lever on said base, adjustable table dogs to actuate said lever, a pair of stop screws positively to limit the movement of said lever and thereby to limit the reciprocatory movement of the table in either direction, a slow-down valve fluid from said cylinder during reversal gradually to slow down the table, an adjustable relief valve. fluid connections between said relief valve and the source of fluid under pressure, means includin fluid connections between said relief valve and the end chambers of said reversing valve whereby positive stopping of the table serves to build up a back pressure to open the relief valve and admit fluid under pressure to an end chamber so as to shift the reversing valve and thereby reverse the direction of movement of the table, and a by-pass valve actuated by reversal of fluid under pressure to said cylinder to by-pass fluid around said slowdown valve at the beginning of the table movement and/ or during reversal to facilitate a rapid starting of the table in the reverse direction.

FRANKLIN E. JOHNSON. 

